As will be recognized by those skilled in the art, during concrete construction, arrays of reinforcement bars ("rebar") are erected within the forms so that when the concrete is poured, the resultant structure is strengthened by the rebar. Typically, intersecting sections of rebar are hand tied to each other with wire. Although it has been known in the prior art to provide various types of hand tools for tying rebar, these tools are cumbersome and unreliable, and hence are not used in the construction industry. To be effective on the job, an applicator tool must be relatively light and easy to handle. It also must be reliable, i.e., able to tie rebar consistently.
Prior art devices tend to be unreliable for several reasons. First, most prior art devices are vulnerable to imperfections in the wire, caused by metal variances, kinks and the like. As a result, the relatively inexpensive and ductile wire used for tying rebar is difficult to reliably feed with mechanical devices. Further, while the wire feed mechanism of such a device must be relatively powerful, the mechanism must not overpower the other working parts by unnecessarily forcing wire and jamming the mechanism. Second, the prior art devices do not yield, on a consistent basis, wire ties that are tight against the rebar. Those loose ties must then be tightened by hand, negating any advantages obtained by using the tool. Finally, prior art devices generally cannot be used for all rebar applications, due to the large size of the rebar encircling means on these devices.
U.S. Pat. No. 4,362,192 includes a rotating mandrel which functions in cooperation with a reciprocal jaw mechanism, but partially because the main jaws are both movable, tying problems are experienced.
U.S. Pat. No. 3,391,715 contemplates a jaw system which provide a looping mechanism, but the jaws are also both movable, leading to tying problems. It also discloses a friction drive wire feed system, which is unreliable, and utilizes clutches to operate the wire feed and looping jaw mechanisms.
U.S. Pat. No. 3,169,559 discloses a system for tying rebar which is complicated by the fact that the applicator head includes rotating ears in the critical region for wire feeding. In other words, the gear rotation and the wire feed occur transversely across an applicator region rather than at the output of a concentric system.
U.S. Pat. No. 4,834,148 discloses a reinforcement binding machine having a pair of applicator jaws and a system for tying wire, but the jaws do not include a pair of fixed members with a captured looping jaw, and the wire feeding mechanism is not concentric with respect to the rotating barrel or mandrel.
U.S. Pat. No. 4,953,598 discloses a hand-held power tool, but the applicator jaw is gear driven in a cumbersome fashion. It also utilizes a jaw assembly to cut the wire.
U.S. Pat. No. 4,498,506 discloses a wire system wherein the wire feeding mechanism is disposed in spaced relation with respect to the applicator head. The wire is fed through a cable so that the power wire feeding apparatus is unnecessarily separated from the critical applicator jaws.
U.S. Pat. No. 4,685,493 integrates the wire spool with the unit body, but does not include reciprocal jaws in the manner of the present invention, nor does it include a reliable drive feed system.
U.S. Pat. No. 4,177,842 includes a feeding mechanism with a reciprocal jaw which attempts to provide looping, but the wire feed points are not controlled through the concentric arrangement proposed by the present invention. The wire is also not crossed as it exits and enters the jaw assembly. Tight ties cannot, therefore, be reliably obtained.
The wire applicator head of U.S. Pat. No. 3,026,915 discloses a rotating mandrel in which a pair of stops can catch wires fed on opposite sides of the mandrel, but lacks the concentric wire feeding system and jaw system herein disclosed.
U.S. Pat. No. 5,217,049 does not cross the wire entering and exiting the jaw assembly. As a result, tight ties cannot reliably be obtained. Further, the wire feed mechanism is not able to feed wire with variations or defects. Clutches are also used to operate the tool, making it unreliable.
Therefore, to date, no portable, light weight tool has been available to tie wire about rebar intersections which can reliably produce tight wire ties and can reliably feed the wire. The tool of the present invention solves these problems.